What is an electronic circuit called that would work like this (for example):
you have a knob the circuit and a servo. you turn the knob and the servo mimics the motion of the knob.

basically I am looking for schematics an information I can use for the control of a simple telemanipulator. just a simple (relatively) copy cat mimic circuit. the controller moves and the manipulator moves. any Ideas what to look for?
is there a name for this type of controller?

I have a couple electronic pachinko machines, a Nishijin "Elfin" and a Daiichi "3-One-Model".

A friend says the knob will only work if the machines are hooked up to a cash machine. That enables a servo or stepper motor, which operates the ball-driving mechanism.

I see the connectors where the cash machine interfaces. My question is, is it a simple job of electrically tying some digital inputs high/low, or would I need to emulate a more complex communication protocol (i.e. "act like a cash machine") to get the knob to work?

Or is there some other way to enable the motor elsewhere on the circuit board. (I am an engineer, so you do not need to simplify the explanation)

Thanks in advance!
Everything works except for the knob. I can load it with balls and shoot them by manually reaching into the back of the machine and flipping the lever. The video works normally, and the machine pays out jackpots.

I think disabling the knob is for security – so the machines cannot easily be tricked into working without the cash machine in the circuit.